This invention relates generally to apparatus and methods for adding one or more selected additives into a mixture and more particularly, but not by way of limitation, to a portable apparatus and a method for mixing a liquid additive and a proppant with a base liquid to prepare at a well site a mixture for use in a well.
During construction activities, for example, mixtures of materials sometimes need to be prepared. With specific reference to drilling and completing an oil or gas well, acidizing and fracturing fluids, as well as cements and gels, sometimes need to be provided at the well site for well-known purposes. Such mixtures can be needed in various quantities and compositions.
To provide such a mixture to a well site, a batch of the anticipated desired composition and quantity can be prepared and then transported to the well site. An example of this is a 4000-gallon bulk acid transport truck. Alternatively, the components of the ultimate mixture can be carried to the well site and there mixed in separate equipment which has also been transported to the well site. These techniques typically produce batches of the mixture. This can produce waste, and expense to the customer, if the well cannot be prepared in time to use the batch or if significantly less than the entire batch is needed in the well. These techniques also typically require more than one piece of equipment to be transported to the well site. This, too, can increase the costs to the customer by way of the additional equipment and the additional manpower to operate it.
In view of these characteristics of the techniques by which mixtures are typically provided to a well site, it would be desirable to provide a technique wherein local mixing "on the fly" (i.e., as the mixture is needed and pumped into the well) would be performed for a specific job. This would obviate the necessity of anticipating ultimate needs and specific timing as must be done when a batch is premixed well before it is actually needed. Creating the needed mixture locally and on the fly would thus likely prevent the waste which can result from the technique whereby a mixture is batched beforehand. To obviate the need for multiple pieces of equipment to be transported separately to the well site, it would also be desirable for the new technique to be a single compact, portable integrated system capable of transporting the needed components, mixing them as needed, and providing control information by which the mixing process can be controlled.
Although it would be desirable to have such a single compact, portable integrated system of any suitable type, it would be preferred to have such a system be versatile so that a variety of mixtures can be produced. This versatility should include the ability to have individual additives or combinations of additives selected for use in producing the mixture. Such versatility should also include the ability to meter one or more selected additives within different, selectable metering ranges. Such versatility should also include the ability to select the location where a selected additive is to be input into the mixing system.
Such an integrated system should also provide for relatively easy control so that operator tasks such as reading and matching meters and consulting additive concentration charts are no longer necessary. For example, where a particulate proppant and one or more liquid additives are to be added into a mixture, computer technology should be used to compute and display a gate setting and actual concentration values. The gate setting would be used to set a proppant gate by which the amount of proppant added into the mixture is controlled, and the actual concentration values would be used to control the metering of the selected additive(s).
Finally, an apparatus and method meeting each of the foregoing needs should preferably also be relatively simple to construct or implement, and require relatively low maintenance and cost.